Fuse



4June 26,1928. P. A. NEWMAN FUSE -Filed Oct. 30, 1924 21 zz 1f 21 3132 z5 17 21 z5 J 2f 33 39 go INVENTOR JszzZHJl/wman @MLA Q4. @r2.4

A TTORNEY.

. )A v l l Patented June 26, 1928.

- UNITED sTATEsP-ATENT ,o1-Fica PAUL A NEwIAN, or PHI'LADELPHIA,

PENNSYLVANIA.

PENNSYLVANIA, Ass'IGNon To muws e NonrHnUP oonPANY, or PHILADELPHIA', PENNSYLVANIA', A oonPonA'rIoN or FUSE.

Appunti@ mea october ao, 1924. semi No. 74am.l

' 10 heat absorbed by the fusible element.

In accordance with my linvention, the fusible element, as a fuse wire or e uivalent, is so spaced from ordisposed wit respect to a hot zone or 15. partake. of the temperature thereof, but .attains, due to heat conducted, radiated. or otherwise transferred from the hot zoneor member, a lower temperature which, how

ever, is augmented by the heat developed '20 within the` usible element itself by the elecltric current traversing it, whereby the fusi- ',ble element attains-a fusing temperature,

causing circuit rupture, when the hot zone or member attains a predetermined tempera(- ture, which, however, is or maybe different from the temperatureat which the fusiblel member melts. a

More particularly in accordance with my,v invention, thefusiblemember vis included in circuit with the resistor or other heating `device ofany heating structure, as -a furnace,

oven, 'electric heater or the like, and is dis-l posed adjacentv orjn'contact with a wall of the heating device or furnace through'which it absorbs heat and -attains a temperature lower than the maximum temperature of the heating devicezor furnace, and thecross section of the fusible elementis so pro ortioned that the current traversing it deve ops sui-j 40 cient heat further to raise itsv temperature,

causing it 'to attainv its fusing temperature,

which may be somewhat less than, .equal to or greater than the maximum temperature of or withinthe heating device orfeurnace, 46 and by preference, the temperature change of the fusibleelement due to the currenttraversing it isrelatively small compared to the temperature'change effected by the heat y yabsorbed from the heating device or fur- 50 nace, whereby the fusewill melt or blo'w atV substantially the same temperature 'of the `-heating elementor furnace, though the curmember that it does not'- .disposed the: hollow rent traversin have'lwidely die Further in accordance it is preferredl that the the 'fusible element -may rent magnitudes.

with my invention, 55. lfusible element be composed of a material having a substantial positive temperature coefficient of resistance,

whereby its rise in'temperature due to heat absorbed from the hot zone ormem- 00 ber increases its resistance, lng the heat develo element itself by t thereby increas- 'ed within the resistance e current traversing it,

whereby as the temperature of the hotf zoneA or member increases, the tem lerature of the 66 .fusible element willincrease ue both to such v. increase 1n temperature cfu-they hot zoneA or element and also `'to-the increase'in the heat generated within-tithe fusible element itself ygthe current as the fusing increase-in the'rateof approach to the fusing temperature. v

My-invention resides in the method and features of` structure and combination of the character. hereinafter described and claimed.

For an understanding of-my method and forms my lforfvan illustration of one of the various pparatus may. take, reference is to be had to the. accompanying drawing, in

which Fig. 1 is a horizontal sectional view-.taken on the line 1 1 of Fi 6. v

Fig. 2 is' a vertica vsectional viewvtaken taken on the Fig. 4 is a cross sectionalfragmental'view taken on the line 4 4 of Fi l "onthe line 2 2 of 1.

Fig. 3 is a cross sectlonal view line 3 3 of Fig. 2.

Fi 5 v1s a cross sectiona viewu i,the hse 5 5 of Fig. 2...

traversing it, to the end that* 70 I temperature is approached the two sources of heat co-operate in effecting' taken on 1 Fig. 6 is a schematicsectionalview ofan fr l electricfurnace showing-the relation between the fusible element andj the heating element.

Referring to the drawing, larly Fig. 6, F represents heated furnace comprising sheet metal or equivalent, within more particuan electrically vthe shell 1, of

which is ,tubular heating or resistor element 13 resting upon the bottomc member 2 member 13 within the shellfl 'is av and closed at its upper end by the rremovable 11d or cover 3. Surrounding the filling of suitable mineral matter or otherr material,

preferably of resistance 14, or equivalent heat-producing' means.

The fuse structure comprises the member or block 15, of lava, porcelain or other equivalent or suitable material, having at its o posite ends the recesses or cavities 16 and 1%. The member 15 is received at lits one end vwithin the exteriorly threaded tubular'member 18, of iron or other suitable material,

having at 18". a shoulder against which the end of the member 15 abuts. The members 15 and 18 project through an opening in/the furnace shell 1, on opposite sides of which Disposed loosely .within the member, 18 is the 'p block or member 18", of libre or other suitare disposed the nuts or collars 19, 19 threaded upon the member18 and between which the shell is c1amped,'for holding the member 18 and the parts carried thereby in position.

able insulating material, in which are disosed and held the blocks or inserts 24,v of rass or other conducting material, having i. the transversely extending holes 26, into which extendthe circuit conductors 27, by which the fusible element 12 isl brought into circuit. Threaded into the blocks 24 arel vthe bindin screws 28, whose heads are accessible throug the aperturesk 29 'in member 18a,

holding the conductors 27, which extend through the op ositely disposed and longitudinally extending slots 20 in the member 18. Extending' longitudinally through the member 15 is the slot 21, within which are disposed side by side thelongitudinally extendingl tubular members or beads 22, of porcelain or equivalent material, each abutting at' itslone end against a block 24. The fusible element 12 ,preferably consists of a conductor or wireof substantially constant cross section, though it will be understood that it may be of changing or varying cross section. In the example illustrated, the fuse wire 12 extends through the members 22 'and has at their right end a free `or exposed portion 12, which shall melt or blow, adapted to lie adjacent or against a wall or 'member13 within or on-the opposite side of which exists the temperature at whose attainment of a predetermined magnitude it is desired that the fuse shall melt or blow.- At its opposite ends the fuse wire 12 extends into holes 30 i'n the blocks 24 and are clamped or held in the position indicated by screws 32, whose heads are accessible through the apertures 31 in the member 18". i i v 70 Each of the members 22 is preferably provide-d with a secondhole or channel in whichl is disposed a member or wire 25, as of constantan or other suitable material, threadedinto a block 24, and serving to support or carry the member 22, or in any event, to relieve the fuse wire l12 of at least a part of the weight of the member 22. f'

Threaded upon one-end of the member 18 is the cap 33, within which is disposed the spring 34 received in the groove 18c of the member 18a and thrusting the latter, the blocks 24, members 22 and the fusible element 12 toward the right, as viewed in Fios. 1 and 2, adjustment of the position of the 85 cap 33 upon ,the member 18 serving to vary the pressure with which the'fusible element 12 engages'the member 13. ,With a kstructure of the character described, a new fuse wire may beintroduced by removal ofthe 90 cap 33 and subsequent withdrawal through the members 18 and 15, which remain in position, of the member 18, which carries the members 22 andthe old or recently blown fuse wire.- By. loosenin the screws `32 the A915 old fuse wire is remove anda new one inserted, and the parts then re-assembled to the osition indicated in Fig. I.

The fusible element 12 may be of any suitable material, but by preference is of sub- |00 stanti/ally pure silver or gold, and b preferenceof 'a material which has a su stantial positive temperature co-eicient of resistance.n Even though silver or gold be used, the fuse is inexpensive because of its'small mass and 105 the 'recovery of a portion of the fuse wire.

The cross section of the fusible element or fuse 12, particularly at the portion 12 thereof which shall blow or fuse, may be anything. suitable or desirable, and by preference is such that the maximum operating current of the circuit will not fuse orblow it Withouty the application of additional heat.

The cross section of the fusible element may be, and in some instances of my practice has been, such that evenv with the maximum furnace-heating current the'rise in temperature'above the ordinary temperature of punity.

Small cross secti'on is further desirable tol reduce the variations and eifectsdue to variations in temperature drop through the heater or furnace wall, as 13, and the variations in thermal contact between the fusible element and the furnace wall. By choosing asuitably small cross section notwithstanding the aforesaid variations in temperature drop and thermal contact, the fuse will melt or blowl at furnace chamber or heater temperatures.

ffuse element shall not comprise parts solwhich differ from each other as little ,as 25 degrees F., though the temperature of the heater or within the furnace chamber may be of the order of 1000 or 1800 degrees F.

It is further desirable that the portion-12 be suitably remote from the blocks 24 and adjacent parts that the heat externally a plied to the portion 12a will encounter su vent the blocks 24 and 'the adjacent partsfrom attaining a temperature which would cause their 4oxidation or deterioration. It is preferable these parts do not attain a temperature exceeding that at which they may be touched by the hands of an operator in replacing a fuse notwithstanding the fact that the furnace or heating element is still at high temperature. l l

It is further desirable that the removable dered, welded or similarly attached to the fuse wire proper, for there is likelihood, particularly under conditions of use herein described, particularly when the fusible ele-- ment per se is short, of suflicient rise of temperature at the welded, soldered or other joint to cause melting or severance from the so applied terminals or parts.

Onev ofthe modes of operation 4 of my system is as follows:

When the heating device o1' furnace is cold and is to be started, the current passing through' the heating device proper, as resistance 14er any other equivalent heat-producing means, is adjusted in magnitude, as by rheostat 4 or any equivalent means, to a suitable maximum, at which, however, the fuse A 12 will not'melt or blow. This effects maximum rate of development of heat, and as the f temperature of the heating element 13 or within'the chamber C approaches the desired v.magnitude, as determinable by the thermocouple 11, or equivalent, and associated temto the heat-absorbed .current through t e perature-indlcatin 'or measurin means, the heating resistance 14 is reduced to such magnitude that thereaftera substantially constant desired temperature within the member 1,3 or chamber C will be maintained. At such redetermined or de-A sired temperature the use will not melt org blow, though it has beenraised in temperature 'by heat absorbed and transmitted to it by or through 'the' member .13. The temperature ofthe fuse wire, particularly at 12, due

by 'it byconduction, radiation orotherwise from jor through the f member' 13, and the heatgenerated within thefuse wire bythe current traversing it, is below thatat which it will l'fuse or melt and open thecircu-it of the heating resistance `14:. The temperature of the fuse wire 12 is, however, preferably near its fusing point for the maximum desired or predetermined temperature-of the ymember 13 or within the cient 'thermal resistance along the wire 12 to pretent to the heat .ber 13 beyond that for the' maximum desired or predetermined temperature causes an increase of resistance in the fuse wire, with the result that lthere is additionally liberated within it more heat by the current traversing it for a given current strength and a further increase if the current strength has increased, whereby the heating effectof the current and the heat-ing effect of the member 13 or chamber C upon the fuse wire operate cumulatively near the fusing temperature of the fuse wire to bring vit rapidly to fusing temperature andf thereby open the circuit. i

The temperature change of the fuse wire is preferably very largely due to the heat absorbed by it, and only to relatively small exgenerated within it'by the current traversing it. The temperature attained by the fuse wire, as at 12", due to absorbedheat, is lower than the maximum desired or predetermined temperature of or within' the member 13 or chamber C, and, in a sense, the CZR heat generated by the current inthe fuse wire more or less compensates or makes up for the difference, whereby the fuse will melt. when the predetermined v desired or maximum temperature is exceeded. The mass or cross section of the fusible ele- 105 ment is preferably made as small as possible, consistent with other circumstances, so that thegfusible elementvmay Aquickly respond to changes or risein temperature andcause the desired operation of circuit rupture as and when described promptly after the predeter mined or ,desired maximum temperature withinthe chamber C or of the member 13 is exceeded. f e The fusible element will blowand' inter- H5 rupt the circuit when the predetermined desired or maximum temperature is exceeded notwithstanding the fact that the currentv traversing it may have-widely different Values.v -For example, the fuse will blow for 12" terials melt or fuse at substantially predeter mined diierent temperatures, and since it is often desirable that, the circuit be openedv upon attainment of a heater or furnace tempera-ture which is different from the temperature of fusion of available fuse material-1. it is generally impossible to choose a fuse of aymaterial which may be subjected directly to the temperature at attainment of which it is desirable the circuit should be opened.

By`recourse to my invention, however, it is possible to locate .the fusible element in such .oo sition o-r beyond Such barrier that it will g subjected to a .substantially lower temperature and yet, by co-action of the current traversing the fusible ele-ment, cause its fusion upon attainment of a predetermined temperature within the heating element or heating zone. So locating the fusible element has the further advantage that its material doesnot deteriorate, as by oxidation, scaling, deformation or other effects which would otherwise result 'if it were subjected 1. The combination with a heating device 'comprising an electric heating element and a wall, of a fuse in circuit with said element and disposed inv position to absorb heat` .from said element substantially exclusively -through said Wall, said fuse having a cross comprising an electric heating element andA sectionl such that its temperature. rise due to the current traversing it is less than its temperature rise due to the heat absorbed from said heating deviee.

th a heating-device 2. The combination w1 I va wall,'of a fuse in circuit with said element and disposed in contact with the outer face -fof'said wall in position to absorb heat from 'sald element' through said Wall, said fuse having` across section such that its tempera.- ture rise due to the current traversing it is less than itstemperature rise due to the heat absorbed from said heating device. Y. 3. The combination with an electric heating' device comprising an electric heating lelement and' a wall, of a fuse in the circuit. of said element and engaging the outer sur-- ,L face of the wall to absorb heat from said element through said wall,l said fuse havingv a positive temperature coeiiicient of resistance anda cross sectlon such that itstemperature rise dueto the current traversing it is less than its temperature rise due to the heat absorbed from said heating device;

4. The combination With an electric heating element, of a fuse in the circuit thereof,

alwall through which heat is absorbed bysaid fuse from said heating relement, a second outer wall remote therefrom, electric'terminal structure to which said fuse is detachably connected, said fuse extending from said terminal structure toward said irst wall and having a portion subjectedto high temperature adjacent said wall, and means for supporting said terminal structure in said second \-\vall, whereby said terminal structure doesv not attain a. temperature preventing interchange of fuses while^said heating element is at high temperature.v

5. The combination with an electric furnace comprising an electric heating element and a wall, of al lfuse in circuit with said element and disposed in engagement with the cooler side of sai'd wall to absorb heat from sai-d element through said( wall, said fuse having such cross sectional ndimensions and coeiiicient of resistance that it will rupture only within acomparatively small range of temperature variation'within said furnace notwithstanding concurrent relatively lar e variations in current through said fuse `an heating element.

6.The comblnation With an electricfurnace comprising an electric heating element and a Wall.'of`a fuse in circuit with said element and resiliently biased into positive heat conducting relation with the cooler sideof said wall for Aabsorb-ing heat from said element through -the wall, and ka heat insulated chamber coacting with said 4wall to substantially enclose the wall-contacting portion of said fuse, thereby concentra-ting heat i upon saidfuse portion. 7. The combination with an electric furnace comprising 'an electric heating element and a wall of refractory material, of anV outer Wall remote from and concentric with said first-named wall, a fuse 'in circuit with said heating elenient detachably supported on said outer wall and biased into resilient engagement with said first-named wall whereby heat absorbed by said fuse from saidlieating element, and to a-much lesser i degree heat due to the current through its own resistance, effects rupture of the fuse within a comparatively small temperature range of said furnace.

. PAUL A. NEWMAN.

10oVI 

